Ad agencies are seeing pockets of weakness across some specific advertiser categories (finance and domestic auto), but the weakness is isolated and not broad-based. [so far]

Search: Google's recent algorithm changes may actually improve revenue growth, but the current environment is showing some signs of demand-related softness.

Display: Some ad networks are seeing flat y/y growth in the US [awful], while international territories are much stronger. Domestic growth is incrementally worse than expected and international incrementally better.

Ad Networks/Ad Exchanges: Advertisers/publishers are starting to question the value of ad networks as they weigh the benefits of brand value versus sheer reach. [About time. Glam Media investors, are you listening? Still comfortable with that $500 million valuation?] Ad exchanges should facilitate more transparency and efficiency in the buying and selling of display ads, and potentially disrupt the legacy blind ad-network business model.

Social Media Monetization: The monetization of social media is difficult (a structural issue), and will remain challenging in the near future.

Web Advertising Spending Has Weakened--RBC

Remarks by advertising executives at an RBC investor dinner suggest that the current optimistic consensus about online advertising in a recession is wrong. US internet display revenue at certain networks is FLAT year over year.